WolfGang,
For your oversized bore in .44, you might look into a company out in St. John, Kansas called Leadheadz. They cast fairly hard bullets and you can specify the bore diameter to an extent. I am guessing that if you went with their largest offering you might get that .44 dialed right in. I have shot a lot of their .430 diameter Keith style bullets in my Super Blackhawk. I loaded them real heavy with H-110 and never had any problems.
Later,
Joe